To join two materials by means of diffusion welding is known in the art. One purpose of joining two materials may be to use materials with different characteristics for any type of mechanical component, such as for instance a rolling bearing. As regards rings of rolling bearings, it may be advantageous to use one material for the raceway surface onto which the rolling elements roll and another material for the core of the ring. One such composite bearing ring is presented in EP1882109B1 comprising a rolling bearing composite ring for an aircraft power plant which ring has been subjected to diffusion welding.